Chocolate Lover's Chocolate Cake - Once Upon a Chef

Ingredients

• 2 cups all-purpose flour, (spooned into measuring cup and leveled-off)
• 2 cups granulated sugar
• 1 cup natural unsweetened cocoa powder, (such as Hershey’s)
• 1 teaspoon salt
• 2 teaspoons baking powder
• 1 teaspoon baking soda
• 2 large eggs, (lightly beaten)
• ½ cup vegetable oil
• 1 cup sour cream
• 1½ teaspoons vanilla extract
• 1 cup boiling water
• 8 ounces semi-sweet or milk chocolate, (broken into small pieces (see note))
• 20 tablespoons (2½ sticks) unsalted butter, softened but still cool
• 1¼ cups confectioners' sugar
• ½ cup natural unsweetened cocoa powder, (such as Hershey’s)
• 1/8 teaspoon salt
• ¾ cup light corn syrup
• 1 teaspoon vanilla extract